1. Field of the Invention
The present invention relates to a device for reproducing and recording a still image. More particularly, the invention is concerned with a still image reproducing apparatus which is intended for use in reproducing a multiplexed signal that includes a composite image signal of a field picture and a recording information, such as date, month and year of the recording or photographing from a recording medium which records such a multiplexed signal, and also with a still image recording apparatus which is designed to be connected to the reproducing apparatus for the purpose of dubbing.
2. Description of the Prior Art
An electronic still camera, as an example of an electronic still image reproducing and recording devices, has been known which is capable of operating in a mode called "field image mode". In this mode, in order to maximize the number of still images recorded in a single magnetic disk, image signals corresponding to a single field is recorded on a single track. In the reproduction of the recorded image, this field image (original field image) is read out alternately with an interpolation field image which is obtained by delaying the original field image by a time which is half the horizontal scanning period H, which is 63.5 usec in the case of an NTSC type system.
The image signal comprising the still image includes various types of information, such as information as to whether the recorded image signal is a field image or a frame image, track No. representing the No. of the track in which each image is recorded, and recording data, such as, date, month and year of the recording. These various types of information which identifies the recorded image will be collectively referred to as ID code, hereinafter.
In the reproduction of the recorded image, the image signal and the ID code are read by a magnetic head and are separated from each other. The ID code is subjected to demodulation by DPSK (Differential Phase Shift Keying) and is decoded in accordance with a timing of a horizontal scanning pulse included in the image signal. The ID code includes a user's area having a plurality of bits, each of which corresponds to 2 or 4 pieces of horizontal synchronizing pulses (HSYNC). For instance, front edges of odd-number horizontal synchronizing pulses H.sub.1, H.sub.2, H.sub.3 . . . shown in FIG. 9(B) are used in determining whether the serial digital signal shown in FIG. 9(A) is of a "H" or "L" level. In the illustrated case, the data carried by this serial digital signal is judged as being "101 . . . ". When the data of a bit is "1", it is judged as being the value which is an inversion of the data of the immediately preceding bit, whereas, when the data is "0", it is judged that the information carried by this bit is the same as that in the immediately preceding bit.
In the case of the image signal of the interpolation field, when the level of the serial digital signal is judged at the timings of the front edges of the odd number horizontal synchronizing signals H.sub.1, H.sub.2, H.sub.3, . . . , only a small margin of 0.5 H, i.e., 31.75 usec, is available with respect to the jitter as will be seen from FIGS. 9(C) and 9(D). Consequently, error is caused in the reading of the recorded information when the rectangular wave is collapsed by the jitter, as shown by the two-dot-and-dash line.
In addition, a deterioration is inevitably caused in the image quality when a dubbed interpolation image signal is reproduced. The deterioration becomes serious as the dubbing is repeated.